Mushoku Tensei: Jobless Reincarnation (Light Novel) Vol. 23

Rudeus's fourth child, Sieghart, is born with the same crop of bright-green hair that Laplace was once feared for. The omen grows ever more ill when a familiar of Perugius's appears and commands Rudeus to bring his newborn son to the floating fortress! Rudeus swears that his plans to fight Laplace are unchanged and that he'll accept any fate for the sake of his family...but will that be enough for Perugius?